You should use
asp:Image[
^] control instead of plain html img tag, like this:
<asp:image runat="server" AlternateText='<%# Eval("title")%>' ImageUrl='/images/htcpic/<%# Eval("image4")%>' Visible='<%# !String.IsNullOrEmpty(Convert.ToString(Eval("image4")))%>' Height="178" Width="120" />